Wow, same for me, with hurt back, and all. I think we might have the same problem. Let's figure out if we really do. I don't have a solution unfortunately, but here is a hint that might be relevant. It took me years to understand that bowing my head deep causes me a headache. To start a bad headache that might last for hours it is enough to look at my own navel for a few seconds. I picked up some slightly unusual habits since I realized this. For example, I pick up dropped objects without looking down, without any conscious effort. If I accidentally bow my head anyway, sometimes it helps if I immediately raise my head high to counteract the first movement. It is metaphor not an explanation, but it feels like blood is rushing to a part of my brain where it is not welcome, and the only way to avoid the headache is to quickly send it back to its proper place.
Another clue: for really bad headaches, it temporarily helps if I push my eyeballs very very hard. Is this the same for you?
Haven't tried pushing on my eyeballs. I will next time I get a headache and report back.
Edit: No effect whatever.
I've been collecting data about my headaches and diet for almost four months now. I don't see any patterns - annoyingly, I get headaches nearly every day, so there's not much information - but I thought I'd post the data set and see if anyone sees anything. Here it is. Hopefully someone finds this an interesting problem.
It's written in note-to-self format (abbreviations like "strawbs" for "strawberries"; if I mention a complicated dish once then I'll shorten it when I eat the leftovers, as "pasta" for "pasta with artichokes and spinach and pesto"; times given approximately and not in a consistent form and often without specifying if they're a.m. or p.m., though they are in chronological order). Quantities aren't given, although if they're suspected to be relevant I may be able to remember specific instances (for unusual foods) or typical portions (for ordinary foods) - other details might also be recollectable similarly. I also don't notice when headaches go away, so I don't know how long they last except when they last all day or become noticeably worse during their course. My sleep schedule varied considerably over this period, but trends more night owl than early bird (for a while I was outright nocturnal). I moved three time zones west at the end of July, should that matter at all.
I'm not soliciting commentary on my diet except insofar as it can be compellingly related to my headaches.
ETA: Assume that every single day I'm drinking lots of skim milk. (2-6 cups depending on how much I eat and how it's spaced out.) There's a couple of exceptions, mostly when I'm in transit for most of a day or run out of milk, but not many and they don't seem to correlate with headaches.